Process and apparatus for forming shaped glass articles

ABSTRACT

A process using a three-piece mold for making a three-dimensionally shaped glass article having a flat area and a curved/bend area is disclosed. The process includes placing a glass sheet on a mold having a shaping surface with a desired surface profile for the shaped glass article including a flat area and a bend area, moving a flat area plunger toward the glass sheet to compress the glass sheet, heating a portion of the glass sheet corresponding to an area above the bend area of the mold to a temperature above a forming temperature, and moving a bend area plunger toward the heated glass sheet to compress the heated glass sheet. A temperature of the glass sheet in the area above the bend area of the mold is higher than a temperature of the glass sheet in the area above the flat area of the mold when compressing the heated glass sheet with the bend area plunger.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 14/269,424filed on May 5, 2014 and benefit of priority under 35 U.S.C. §120 ishereby claimed. U.S. application Ser. No. 14/269,424 claims the benefitof priority under 35 U.S.C. §119 of U.S. Provisional Application Ser.No. 61/820,363 filed on May 7, 2013 and U.S. Provisional ApplicationSer. No. 61/951,585 filed on Mar. 12, 2014, the content of each isrelied upon and incorporated herein by reference in its entirety.

BACKGROUND

1. Field

The present disclosure relates to forming shaped glass articles, forexample covers for mobile or handheld electronic devices.

2. Background

Covers for handheld devices are required to be aesthetically pleasingwhile being functional. There is also a growing trend to havethree-dimensionally shaped covers, wherein a portion of the cover isflat and another portion is shaped, for example having a bend or curve.Glass is one of the materials that can be used to make such covers;however processes and apparatuses are needed to form shaped glassarticles having a flat region and a bend region. The present disclosurerelates to processes and apparatuses for forming shaped glass articleswith attributes that make them useful as cover glasses.

SUMMARY

A first aspect includes making a three-dimensionally shaped glassarticle, including placing a glass sheet in a forming tool, wherein theforming tool includes a mold having a shaping surface with a desiredsurface profile for the shaped glass article including a flat area and abend area, a flat area plunger having a shaping surface corresponding tothe flat area of the mold, and a bend area plunger having a shapingsurface corresponding to the bend area of the mold. The process alsoincludes moving the flat area plunger toward the glass sheet to compressthe glass sheet, heating a portion of the glass sheet corresponding toan area above the bend area of the mold to a temperature above a formingtemperature, and moving the bend area plunger toward the heated glasssheet to compress the heated glass sheet, thereby forming a shaped glassarticle having a flat area and a bend area. A temperature of the portionof the glass sheet in the area above the bend area of the mold is higherthan a temperature of a portion of the glass sheet in an area above theflat area of the mold when compressing the heated glass sheet with thebend area plunger.

In some embodiments, the mold, the flat area plunger, and the bend areaplunger are porous. In some embodiments, a gas flows through the porousmold, flat area plunger, and bend area plunger to form a compressive gaslayer above and below the glass sheet. In some embodiments, the bendarea plunger provides the heat for heating the portion of the glasssheet corresponding to the area above the bend area of the mold. In someembodiments, a radiant heater provides the heat for heating the portionof the glass sheet corresponding to the area above the bend area of themold.

In some embodiments, the bend area of the mold includes a first bendarea and a second bend area. In some embodiments, the bend area plungeris a first bend area plunger arranged above the first bend area of themold and wherein the forming tool also includes a second bend areaplunger arranged above the second bend area of the mold. In someembodiments, the flat area of the mold includes a first flat area and asecond flat area. In some embodiments, the flat area plunger is a firstflat area plunger arranged above the first flat area of the mold and theforming tool also includes a second flat area plunger arranged above thesecond flat area of the mold.

In some embodiments, a portion of the glass sheet compressed between theflat area plunger and the mold is held at a viscosity in a range from10¹² P to 10^(13.7) P. In some embodiments, a portion of the glass sheetbetween the flat area plunger and the mold is compressed in a range from10 kPa to 1 MPa. In some embodiments, a portion of the glass sheetcompressed between the bend area plunger and the mold is held at aviscosity in a range from 10^(9.6) P to 10¹¹ P. In some embodiments, aportion of the glass sheet between the bend area plunger and the mold iscompressed in a range from 10 kPa to 1 MPa.

A second aspect includes an apparatus for making a three dimensionallyshaped glass article having a mold having a shaping surface with adesired surface profile for the shaped glass article including a flatarea and a bend area, a flat area plunger positioned over the flat areaof the mold and having a shaping surface corresponding to the flat areaof the mold, a bend area plunger positioned over the bend area of themold and having a shaping surface corresponding to the bend area of themold, and a heater positioned to heat a region of a glass sheet placedover the bend area of the mold, wherein the flat area plunger and thebend area plunger move relative to one another.

In some embodiments, the mold, the flat area plunger, and the bend areaplunger are porous. In some embodiments, a gas source is connected tothe porous mold, flat area plunger, and the bend area plunger so thatgas can flow through the porous mold, flat area plunger, and bend areaplunger to form a compressive gas layer above and below the glass sheet.In some embodiments, the heater is incorporated in the bend areaplunger. In some embodiments, the heater is a radiant heater positionedadjacent the bend area plunger.

In some embodiments, the bend area of the mold includes a first bendarea and a second bend area. In some embodiments, the bend area plungeris a first bend area plunger arranged above the first bend area of themold and wherein the apparatus also includes a second bend area plungerarranged above the second bend area of the mold. In some embodiments,the flat area of the mold includes a first flat area and a second flatarea. In some embodiments, the flat area plunger is a first flat areaplunger arranged above the first flat area of the mold and the apparatusalso includes a second flat area plunger arranged above the second flatarea of the mold.

A third aspect includes a 3D glass structure formed by the processdescribed above.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and are intended toprovide an overview or framework for understanding the disclosure. Theaccompanying drawings are included to provide a further understandingand are incorporated in and constitute a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a description of the figures in the accompanyingdrawings. The figures are not necessarily to scale, and certain featuresand certain views of the figures may be shown exaggerated in scale or inschematic in the interest of clarity and conciseness.

FIGS. 1A-1B show examples of a dish shaped glass cover and a sled shapedglass cover, respectively.

FIGS. 2A-2B show an exemplary cross-sectional view of a shaped glassarticle having a spline radius typical for consumer electronicsapplications, where the glass bend radius decreases towards the edge.

FIGS. 3A-3C show exemplary three 3D shaped glass sheets over a grid,formed by two mold pressing, vacuum sagging, and machining,respectively. The grid reflection shows how the glass surface distortsthe transmission of light due to inherent process issues in making the3D parts via two-mold pressing, one-mold vacuum sagging, and machining.

FIGS. 4A-4D show the optical distortion caused by buckling of the glasssheet (FIGS. 4A-4B) and stretching of the flat region into a corner(FIGS. 4C-4D) in a conventional two-mold pressing process.

FIG. 5 shows deviation of the glass sheet in a corner region from adesired shape in a conventional two-mold pressing process.

FIGS. 6A-6D shows the distortion mechanism caused by buckling of theglass sheet in a one-mold process using vacuum only, or vacuum andpressure forming.

FIGS. 7A-7E show an exemplary schematic of a bend press process using athree-piece mold.

FIG. 8 is an exemplary cross-sectional view of a three-piece mold.

FIG. 9 pictorially describes the gap between the glass and bottom moldto (1) avoid overpressing marks on the bend area of the glass, (2)prevent cosmetic damage on a concave side of the bend where defects aremore difficult to polish, and (3) compensate for initially fastercontraction of the glass after pressing relative to the mold.

FIGS. 10A-10E is an exemplary schematic of a bend press process using aporous three-piece mold.

FIG. 11 is a graph showing a thermal cycle comparison between aconventional isothermal press and a three-piece mold bend press.

FIG. 12A-12D is an exemplary schematic of a bend press process using aporous two-piece mold.

FIG. 13 is a graph showing a pressure profile across the width of theglass using a two-piece mold bend pressing process.

FIG. 14 is a graph showing a pressure profile across the width of theglass using a three-piece mold bend pressing process.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details may beset forth in order to provide a thorough understanding of embodimentsdescribed herein. However, it will be clear to one skilled in the artwhen embodiments may be practiced without some or all of these specificdetails. In addition, like or identical reference numerals may be usedto identify common or similar elements.

Disclosed are materials, compounds, compositions, and components thatcan be used for, can be used in conjunction with, can be used inpreparation for, or are embodiments of the disclosed method andcompositions. These and other materials are disclosed herein, and it isunderstood that when combinations, subsets, interactions, groups, etc.of these materials are disclosed that while specific reference of eachvarious individual and collective combinations and permutation of thesecompounds may not be explicitly disclosed, each is specificallycontemplated and described herein.

As used herein, the term “about” means that amounts, sizes,formulations, parameters, and other quantities and characteristics arenot and need not be exact, but may be approximate and/or larger orsmaller, as desired, reflecting tolerances, conversion factors, roundingoff, measurement error and the like, and other factors known to those ofskill in the art. In general, an amount, size, formulation, parameter orother quantity or characteristic is “about” or “approximate” whether ornot expressly stated to be such.

The term “or”, as used herein, is inclusive; more specifically, thephrase “A or B” means “A, B, or both A and B”. Exclusive “or” isdesignated herein by terms such as “either A or B” and “one of A or B”,for example.

The indefinite articles “a” and “an” are employed to describe elementsand components of embodiments. The use of these articles means that oneor at least one of these elements or components is present. Althoughthese articles are conventionally employed to signify that the modifiednoun is a singular noun, as used herein the articles “a” and “an” alsoinclude the plural, unless otherwise stated in specific instances.Similarly, the definite article “the”, as used herein, also signifiesthat the modified noun may be singular or plural, again unless otherwisestated in specific instances.

It is noted that terms like “preferably,” “commonly,” and “typically,”when utilized herein, are not utilized to limit the scope or to implythat certain features are critical, essential, or even important to thestructure or function of the disclosure. Rather, these terms are merelyintended to identify particular aspects of an embodiment or to emphasizealternative or additional features that may or may not be utilized in aparticular embodiment of the present disclosure.

It is noted that one or more of the claims may utilize the term“wherein” as a transitional phrase. For the purposes of the disclosure,it is noted that this term is introduced in the claims as an open-endedtransitional phrase that is used to introduce a recitation of a seriesof characteristics of the structure and should be interpreted in likemanner as the more commonly used open-ended preamble term “comprising.”

GORILLA® GLASS is used as cover glass in consumer electronics because ofits outstanding mechanical properties. The high strength and damageresistance of GORILLA® GLASS are of interest for consumer electronics,especially handhelds and touch screen applications because of scratchand damage resistance when the device is dropped or otherwisemechanically impacted in daily use. In most applications, cover glass istwo-dimensional (i.e., flat). But there has been a large customer pullfor three-dimensionally shaped glass for both front and back phonecovers driven by industrial design. For example, touch screens anddisplays integrated with glass shapes having a large flat area andcurved sections that wrap around device edges have been of mostinterest. FIG. 1A illustrates an exemplary shaped cover glass 100 ahaving a dish shape such that a top surface has a flat (or nearly flat)region 102 a in the middle bounded by four bent/curved sides 104 a. FIG.1B illustrates another exemplary shaped cover glass 100 b having a sledshape such that a top surface has a flat (or nearly flat) region 102 bin the middle bounded by four sides, wherein two of the sides 104 b,which oppose each other, are bent/curved.

FIG. 2A is an exemplary cross sectional view of a shaped glass article200 made according to the processes described herein having a front orback cover glass section 202 that can be substantially flat and a sidecover glass section 204. Flat regions 102 a, 102 b of shaped cover glass100 a, 100 b can serve as front or back cover glass section 202 andcurved/bent sides 104 a, 104 b of shaped cover glass 100 a, 100 b canserve as a side cover glass section 204. Small bend radii (0.5-5 mm) forside cover glass section 204 are desirable to maximize the display areaof the cover glass, while still achieving a wraparound shape. Bend radiithat decrease towards the edge can also be desirable to achieve aseamless transition between glass and bezel. As shown for example inFIG. 2B, bend radii R1, R2, and R3 decrease along a transition from flatfront or back cover glass section 202 to the curved/bent side coverglass section 204, wherein R1 is closest to front or back cover glasssection 202, R3 is closest to an edge 206 of curved/bent side coverglass section 204, and R2 is in between R1 and R3. In some embodiments,R3 can be in a range from about 0.5 mm to about 5 mm.

The shapes described above with respect to FIGS. 1A-2B are quitechallenging to form in glass by either thermal forming or glassmachining. Thermal forming can include heating a flat two-dimensionalglass sheet and (1) pressing the glass between two complementary shapedmolds (“two mold pressing”) or (2) pulling a vacuum to cause the glassto conform to the shape of a mold (“vacuum sagging”). A common defectfrom two mold pressing or vacuum sagging is optical distortion in theglass which can be observed in the reflection of a grid as shown in FIG.3A for two mold pressing and in FIG. 3B for vacuum sagging. Also, asshown in FIG. 3C, glass machining can result in optical distortions. Itis not possible to fully remove all machining marks near the corners andtight bends when polishing a concave side of such a glass shape, and itis quite challenging to achieve even polish over curved sections withoutoptical distortions.

The optical distortion from two mold pressing can be caused by bucklingin the forming process as shown for example in FIGS. 4A-4D. FIG. 4Aillustrates a glass sheet positioned in a two mold press before heat andpressure application. FIG. 4B illustrates the buckling that occurs tothe section of the glass that is intended to be flat during the heatingand pressing. FIG. 4C illustrates a simulation measuring the bucklingeffect in the flat region in plan view and measures the deviation inmillimeters of a glass sheet from a desired shape. FIG. 4D illustratesthe measuring of the buckling effect in a cross sectional view alongline A-A in FIG. 4C from a desired shape in millimeters. Also, thinningcan occur in the corners during two mold pressing because the glass isstretched to form the shape of the corners. This is illustrated forexample in FIG. 5, which illustrates a simulation measuring a deviationin millimeters of a shaped glass article from a desired shape in thecorner region.

The optical distortion from vacuum sagging can also be caused bybuckling in the forming process as shown for example in FIGS. 6A-6C,which illustrate the shape of the glass at different points during theprocess. As can be seen in FIG. 6C, buckling occurs by the curved/bentregions. This is also shown in FIG. 6D, which measures a deviation of ashaped glass article from a desired shape at various points along awidth of the shaped glass article taken at four locations along thelength of the shaped glass article. The y axis measures the deviation inmillimeters and the x axis measures the distance along the width of theshaped glass article from the center (zero on the x axis). The arrowspoint to the areas of the shaped glass article corresponding to thegreatest deviation.

The processes and apparatuses described herein address the cosmetic anddistortion issues in the flat area when forming a three-dimensionallyshaped glass article, and enable precision forming tight bend radii andcomplex splines. For example, the use of a forming tool having athree-piece mold for shaping the glass can overcome, or minimize, theproblems discussed above. A three-piece mold can include a bottom moldhaving a shaping surface corresponding to a desired surface profile of ashaped glass article including a flat area and a bend area; a flat areaplunger having a shaping surface corresponding to the flat area of themold and positioned above and aligned with the flat area of the mold;and a bend area plunger having a shaping surface corresponding to thebend area of the mold and positioned above and aligned with the bendarea of the mold. The three-piece mold configuration allows for heatingdifferent portions of the glass to different temperatures during theshaping process and/or applying different pressures to differentportions of the glass. Thus, the three-piece mold allows for a varyingtemperature and/or pressure profile across the width of the glass. Forexample, the portion of the glass shaped by the bend area plunger can beheated to a higher temperature by heating the bend area plunger and havemore pressure applied to it than the portion of the glass under the flatarea plunger by applying more compressive force with the bend areaplunger than the flat area plunger.

FIGS. 7A-7E and FIG. 8 illustrate an exemplary embodiment of the presentdisclosure for forming a three-dimensional (“3D”) shaped glass articlehaving a flat region and a curved/bend region. FIGS. 7A-7E illustrate anexemplary step by step view of the process using a three-piece mold.FIG. 8 is a cross-sectional view showing more detail of the exemplarythree-piece mold shown in FIGS. 7A-7E. A 3D cover glass can be made bythermally reforming the shaped glass from a two-dimensional (“2D”) flatglass sheet. In some embodiments, the 2D glass sheet can be extractedfrom a pristine sheet of glass formed by a fusion process. The pristinenature of the glass can be preserved up until the glass is subjected toa strengthening process, such as an ion-exchange chemical strengtheningprocess.

First, a 2D glass sheet 700 can be placed on a mold 710 in a formingtool. Mold 710 can have a shaping surface 712 with a desired surfaceprofile of a shaped glass article including a flat area 714 and a bendarea 716. (FIG. 7A) In some embodiments, mold 710 can include alignmentpins 818 for accurately positioning the glass sheet on mold 710. In someembodiments, glass sheet 700 can be preheated before being placed in theforming tool. For example, glass sheet 700 can be preheated using anair-bearing preheat station wherein, for example, glass sheet 700 can beheated to about 600° C. for a cycle time of less than about 60 seconds.In other embodiments, mold 710 can be placed in a furnace and glasssheet 700 can be convection heated. This allows mold 710 to be at orclose to the forming temperature and minimizes the time glass sheet 700is on mold 710, thus lowering the manufacturing cost. In someembodiments, the furnace enclosure can be an inert or vacuum atmosphere,or an ambient atmosphere. Use of a vacuum or inert atmosphere canprovide increased cleanliness.

Next, mold 710 can be indexed into a press station where a region of theglass sheet corresponding to the flat region of the finished shapedglass article is placed under compression. (FIG. 7B) This can beaccomplished using a flat area plunger 720 having a shaping surface 722corresponding to flat area 714 of mold 710. Mold 710 and/or flat areaplunger 720 move to compress glass sheet 700. In some embodiments, aservo driven actuator 813, 823 moves mold 710 and/or flat area plunger720 with a precisely controlled speed, for example, in a range fromabout 0.01 mm/sec to about 10 mm/sec. In some embodiments either flatarea plunger or mold 710 are stationary while compressing the region ofglass sheet 700 corresponding to the flat region of the finished shapedglass article. In some embodiments, the region of glass sheet 700corresponding to the flat region of the finished shaped glass articlecan be compressed at a pressure from about 10 kPa to about 1 MPa. Insome embodiments, the heat and pressure applied to the region of glasssheet 700 corresponding to the flat region of the finished shaped glassarticle hold the flat region at a viscosity in a range from about 10¹² Pto about 10^(13.7) P.

Next, the region of glass sheet 710 corresponding to the bend region ofthe finished shaped glass article can be heated to above a formingtemperature of glass sheet 710, which is a temperature at which glasssheet 710 can be formed to a desired shape. (FIG. 7C) In someembodiments, radiant heaters 730 can provide the heat to obtain theforming temperature. In some embodiments, the bend region can be heatedfor about 10 seconds or less to reach the forming temperature.

Next, a bend area plunger 740 having a shaping surface 742 correspondingto bend area 716 of mold 710 is lowered toward glass sheet 710. (FIG.7D) Bend area plunger 740 can surround an outer perimeter of flat areaplunger 730 and moves independently from flat area plunger 730. In someembodiments, bend press plunger 740 can provide the heat for heating thebend region to the forming temperature in addition to or instead ofradiant heaters 730. In such instances, bend press plunger 740 caninclude a heater 844. In some embodiments, the region of glass sheet 700corresponding to the bend region can be heated to the formingtemperature while the region of glass sheet 700 corresponding to theflat region is not heated to the forming temperature. This is oneadvantage of a three-piece mold over two-piece molds and vacuum saggingbecause it allows for varying a temperature and/or pressure profileacross the width glass sheet 700. Since glass sheet 710 can be flat whenplaced on mold 710, the region of glass sheet 700 corresponding to theflat region is kept below the forming temperature of glass sheet 700.This can be accomplished by not directly heating the region of glasssheet 700 corresponding to the flat region. Also, to counteract theeffect of heat from the bend region dissipating to the flat region, flatregion 714 of mold 710 can include and/or flat area plunger 730 caninclude a cooling chamber 815, 825 respectively. In some embodiments,bend area plunger 740 can be driven by upper servo actuator with aprecisely controlled speed, for example, in a range of from about 0.01mm/sec to about 10 mm/sec. In some embodiments, the region of glasssheet 700 corresponding to the bend region of the finished shaped glassarticle can be compressed at a pressure from about 10 kPa to about 1MPa. In some embodiments, the heat and pressure applied to the region ofglass sheet 700 corresponding to the bend region of the finished shapedglass article hold the bend region at a viscosity that is sufficientlylow to prevent high stress when the bend region is formed, but stillhigh enough to prevent cosmetic defects and mold marks to transfer toglass sheet 700, for example, in a range from about 10^(9.6) P to about10¹¹ P.

The bend regions in the shaped glass article can be formed by movingbend area plunger 740 downward with a precisely controlled speed until adesired force or position is achieved. In some embodiments, heat is nolonger supplied and the bends are held under compression to relievestress and prevent snap back, while they cool. (FIG. 7E) The processillustrated in FIGS. 7A-7E is merely exemplary and the process caninclude additional steps.

In some embodiments, to prevent glass scuffing and mold marks on theconcave side of the bends, shaping surface 712 of mold 710 can beundersized by about 100 μm to about 200 μm in bend area 716, as shownfor example in FIG. 9, so that there is a gap g between the bend regionof glass 700 and bend area 716. Shaping surface 712 also needs to beundersized to compensate for the differential thermal expansion of glassand the mold material. In the visco-elastic regime, glass expansionrapidly increases and exceeds that of the mold material. As the glasscools, the thermal expansion of glass is less or close to that of commonmold materials that can be used for pressing, such as coated nickelsuperalloys (Inconel, Hastalloy, etc.), graphite, silicon carbide ortungsten carbide.

In some embodiments, the mold, flat area plunger, and bend area plungercan be porous and connected to a pressurized gas source. This permitsthe formation of a compression gas layer between the glass sheet and themold, flat area plunger, and bend area plunger such that the glass sheetdoes not contact the mold, flat area plunger and bend area plunger. Thiscan be advantageous because contact between the glass sheet and themold, flat area plunger, and bend area plunger can cause cosmeticdefects on the shaped glass article. Also typical materials for moldpieces, such as nickel alloy, need to be refinished or recoated afterevery few hundred cycles as a result of contact with the hot glass. Thepresence of the compression gas layers between the glass sheet and themold, flat area plunger, and bend area plunger can minimize or eliminatethese problems because the glass sheet does not contact the mold pieces,and thereby extends the mold life.

FIGS. 10A-10E illustrate an exemplary process for forming athree-dimensional (“3D”) shaped glass article having a flat region and acurved/bend region that is analogous to the process shown in FIGS. 7A-7Eexcept that, as described below, mold 710′, flat area plunger 720′, andbend area plunger 740′ are porous. Mold 710′, flat area plunger 720′,and bend area plunger 740′ can be connected to a pressurized chemicallyinert gas source, such as, but not limited to, nitrogen or argon. Thegas can flow from the gas source through mold 710′, flat area plunger720′, and bend area plunger 740′ to shaping surfaces 712′, 722′ and742′, respectively. In some embodiments, each of mold 710′, flat areaplunger 720′ and bend area plunger 740′ can be made from a porousmaterial, such as, but not limited to, metal, graphite, or mullite. Insuch embodiments, mold 710′, flat area plunger 720′, and bend areaplunger 740′ can be manufactured so that along the perimeter of each,there is only pores on shaping surfaces 712′, 722′, and 742′ andsurfaces connected to the pressurized gas source. In other embodiments,mold 710′, flat area plunger 720′ and bend area plunger 740′ can be madeof a nonporous material, such as, but not limited to, stainless steel ornickel, and a matrix of holes can be drilled into mold 710′ flat areaplunger 720′ and bend area plunger 740′ to provide pores between thepressurized gas source and shaping surfaces 712′, 722′, and 742′. Insome embodiments, the pores can be sized to avoid imprinting marks onthe glass surface. In some embodiments, mold 710′, flat area plunger720′ and bend area plunger 740′ can be made of an anisotropic material.

The flow of the gas through mold 710′ can be at a sufficient flow rateand/or pressure to form a layer of gas between shaping surface 712′ anda glass sheet that acts as a bed of gas capable of holding the glasssheet, as shown for example in FIG. 10A. The flow of the gas throughflat area plunger 720′ can be at a sufficient flow rate and/or pressureto form a layer of gas between shaping surfaces 722′ and the glass sheetto provide a compressive force sufficient to maintain the flatness ofthe glass sheet, as shown for example in FIG. 10B. Similarly, the flowof the gas through bend area plunger 740′ can be at a sufficient flowrate and/or pressure to form a layer of gas between shaping surface 742′and the glass sheet to provide a compressive force sufficient to createa bend region in the glass sheet, as shown for example in FIG. 10E.

The thickness of the gas layers can vary depending on the local airbearing response, but in some embodiments can be on an order of about 1micron, about 10 microns, about 100 microns, or more. The thickness ofeach gas layer can be the same or different. For example, the thicknessof the gas layer between flat area plunger 720′ and mold 710′ can bedifferent than the thickness of the gas layer between bend area plunger740′ and mold 710′. The compressive force or load exerted by each gaslayer can vary along a length of the gas layer. In some embodiments, thegas can be heated. In some embodiments, as discussed above, a benefit ofthe “three-piece” mold is that it allows for varying the pressureprofile across the width of the glass. As such, in some embodiments, thecompressive force or load of each gas layer and the thickness can bedifferent; and in other embodiments they can be the same.

In some embodiments, a cross-sectional view of the three piece moldassembly shown in FIGS. 10A-10E can be the same as that shown in FIG. 8except that mold 710′, flat area plunger 720′ and bend area 740′ havepores and there is tubing to deliver the gas from a gas source. In someembodiments, a compressor is connected to the gas source upstream of themold. In some embodiments, the gas can be supplied at a constantpressure through a pressure regulating device. In other embodiments, thegas can be supplied at constant flow using an active controller thatadjusts the pressure to provide constant gas flow.

While FIGS. 10A-10E, illustrate each of mold 710′, flat area plunger720′, and bend area plunger 740′ being porous, this is merely exemplary.Any combination of porous and nonporous mold pieces can be used.

FIGS. 7A-7E, 8, and 10A-10E, illustrate a three-piece mold, however, insome embodiments, depending upon the desired shape of the glass article,the forming tool can include a four-piece mold, a five-piece mold, asix-piece mold, or more. In some embodiments, the forming tool wouldhave more than three mold pieces if the edge of the shaped glass articlehas more than two bends/curves. In such an instance, there could be afirst bend area plunger for the first bend region positioned above andaligned with a corresponding first bend region on the mold's shapingsurface and a second bend area plunger for the second bend regionpositioned above and aligned with a corresponding second bend region onthe mold's shaping surface. In other embodiments, if the desired shapeof the glass article has multiple non-contiguous flat areas with bendarea in between, then the forming tool can include a flat area plungerfor each flat area and a bend area plunger for each bend area.

Further process techniques and methods that may be applicable to theprocesses described herein include those described in U.S. PatentApplication Publication No. 2010/0000259 (Ukrainczyk, “Method of MakingShaped Glass Articles”), European Patent Application No. 10306317.8,which published as European Patent Application EP2457881 (CorningIncorporated, “Method and Apparatus for Bending a Sheet of Material intoa Shaped Article”), U.S. patent application Ser. No. 13/480,172, whichpublished as U.S. Patent Application Publication No. 2012/0297828(Bailey et al., “Glass Molding System and Related Apparatus andMethod”), U.S. Provisional Application No. 61/545,332 to which U.S.patent application Ser. No. 13/647,043 claims the benefit, whichpublished as U.S. Patent Application Publication No. 2013/0086948(Bisson et al., “Apparatus and Method for Tight Bending Thin GlassSheets”), and U.S. Provisional Application No. 61/545,329, to which PCTApplication No. PCT/US12/58950 claims the benefit, which published asWIPO Publication No. WO 2013/05589 (Bisson et al., “Reshaping Thin GlassSheets”) all incorporated by reference. The 2D glass sheet can be madeby any known process, including rolling, fusion, float, etc.

As discussed above, in some embodiments, the front cover glass sectionof the 3D cover glass (e.g., 202) is flat. In some embodiments, the flatfront cover glass has a flatness of better than ±10 μm, ±25 μm, ±50 μm,±75 μm, ±100 μm, ±125 μm, ±150 μm, ±100 μm, ±200 μm, ±250 μm, ±300 μm,or ±400 μm over a 25 mm×25 mm area, as measured by a FlatMaster® tool.In one embodiment, the flat front cover glass section has a flatness ofbetter than ±100 μm over a 25 mm×25 mm area, as measured by aFlatMaster® tool. In other embodiments, the front cover glass sectioncan be curved.

In some embodiments, each side cover glass section of the 3D cover glass(e.g., 204) includes a bend. The bend angle and radius can be selectedbased on the peripheral side geometry of the electronic device. In oneembodiment, the bend angle is in a range from greater than 0 to 90°. Insome embodiments, the bend radius is greater than 1 mm. In someembodiments, the bend radius is about 0.25, 0.5, 0.75, 1.0, 1.25, 1.5,1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0,10.0, 15.0, 20.0 mm or more. In some embodiments, the bend is a complexbend that has a changing radius, such as described by a Burmester curve.In an alternate embodiment, the bend angle can be greater than 90°.

In some embodiments, the 3D cover glass has a uniform wall thicknesstypically in a range from 0.3 mm to 3 mm. In some embodiments, thethickness is about 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2,1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6,2.7, 2.8, 2.9, or 3.0. In one embodiment, the total variation in thewall thickness of the cover glass wall is within ±100 μm. In anotherembodiment, the total variation in the wall thickness of the cover glasswall is within ±10 μm, ±20 μm, ±30 μm, ±40 μm, ±50 μm, ±60 μm, ±70 μm,±80 μm, ±90 μm, ±100 μm, ±125 μm, ±150 μm, ±200 μm, or ±250 μm.

The 3D cover glass has an inside surface and an outside surface. Whenthe 3D cover glass is placed on an electronic device, the inside surfacewould be on the inside of the assembly, whereas the outside surfacewould be on the outside of the assembly. Each surface is smooth, andthis smoothness can be characterized by surface roughness. In oneembodiment, the average surface roughness (Ra) of each surface of the 3Dcover glass is less than 1 nm. In another embodiment, the averagesurface roughness (Ra) of each surface of the 3D cover glass is lessthan 0.7 nm. In some embodiments, the average surface roughness (Ra) ofeach surface of the 3D cover glass is less than 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9,2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0 nm. In anotherembodiment, the average surface roughness (Ra) of at least one of thesurfaces of the 3D cover glass is less than 0.3 nm. In some embodiments,the average surface roughness (Ra) of at least one of the surfaces ofthe 3D cover glass is less than 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2,2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0 nm.

The surface roughnesses of the inside and outside surfaces can be thesame or different. The latter can be the case, for example, if the 3Dcover glass is made by a mold and only one of the surfaces comes intocontact with the mold during forming of the 3D cover glass. Typically,the surface of the 3D cover glass contacting the mold will be theoutside surface. However, it is possible to design the mold such thatthe surface of the 3D cover glass not contacting the mold will be theoutside surface.

In some embodiments, the surfaces of the 3D cover glass are essentiallyflawless. By “essentially flawless,” it is meant that there are noindentations (or dimples) larger than 150 μm in diameter, as measured byan optical microscopy technique, in the surfaces. In some embodiments,there are less than an average of 50, 40, 30, 20, 10, 5, 4, 3, 2, or 1indentations (or dimples) larger than 150 μm in diameter in an 25 mm×25mm area on any of the surfaces, as measured by optical microscopy.

In some embodiments, the 3D glass is transparent and has an opticaltransmission greater than 85% in a wavelength range of 400 nm to 800 nm.In some embodiments, the 3D cover glass is transparent and has anoptical transmission greater than 75%, 80%, 85%, 87%, 90%, 93%, 95%,97%, or 99% in a wavelength range of 400 nm to 800 nm.

A coating can be deposited on a surface of the 3D cover glass to make aportion of the 3D cover glass semi-transparent or opaque. The portion ofthe 3D cover glass in which the coating is not deposited can be a clearaperture on the front cover glass section, which would allow for viewingof and interaction with an electronic device display.

In some embodiments, the 3D cover glass is resistant to damage in termsof compressive stress. In some embodiments, the compressive stress atsurface of the glass is greater than 300 MPa. In one embodiment, thecover glass has a compressive stress greater than 250, 300, 350, 400,450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000 MPa or more.The 3D cover glass (or the 2D glass sheet used in making the 3D coverglass) can be subjected to a strengthening process to achieve thecompressive stress that is greater than 300 MPa. In some embodiments,the 3D cover glass is subjected to an ion-exchange chemicalstrengthening process to achieve a combination of a compressive stressgreater than 300 MPa and an ion-exchange depth of layer of at least 25μm. In some embodiments, the ion-exchange depth of layer is at least 10,15, 20, 25, 30, 35, 40, 45, or 50 μm. The ion-exchange depth of layer ismeasured from a surface of the glass into the glass. An ion-exchangedlayer is characterized by the presence of oversized ions in the glasslattice structure.

In some embodiments, the 3D cover glass is resistant to damagecharacterized in terms of hardness and/or scratch resistance. In oneembodiment, the 3D cover glass has a hardness greater than 7 on the Mohsscale. In some embodiments, the 3D cover glass has a hardness of about6, 6.3, 6.5, 6.7, 7.0, 7.3, 7.5, 7.7, 8, 8.3, 8.5, 8.7, or 9 on the Mohsscale.

As a result of the raw materials and/or equipment used to produce theglass compositions described herein, certain impurities or componentsthat are not intentionally added can be present in the final glasscomposition. Such materials are present in the glass composition inminor amounts and are referred to herein as “tramp materials.”

As used herein, a glass composition having 0 mol % of a compound isdefined as meaning that the compound, molecule, or element was notpurposefully added to the composition, but the composition may stillcomprise the compound, typically in tramp or trace amounts. Similarly,“iron-free,” “alkali earth metal-free,” “heavy metal-free” or the likeare defined to mean that the compound, molecule, or element was notpurposefully added to the composition, but the composition may stillcomprise iron, alkali earth metals, or heavy metals, etc., but inapproximately tramp or trace amounts.

In some embodiments, the 3D cover glass is made from an alkalialuminosilicate glass composition. An exemplary alkali aluminosilicateglass composition comprises from about 60 mol % to about 70 mol % SiO₂;from about 6 mol % to about 14 mol % Al₂O₃; from 0 mol % to about 15 mol% B₂O₃; from 0 mol % to about 15 mol % Li₂O; from 0 mol % to about 20mol % Na₂O; from 0 mol % to about 10 mol % K₂O; from 0 mol % to about 8mol % MgO; from 0 mol % to about 10 mol % CaO; from 0 mol % to about 5mol % ZrO₂; from 0 mol % to about 1 mol % SnO₂; from 0 mol % to about 1mol % CeO₂; less than about 50 ppm As₂O₃; and less than about 50 ppmSb₂O₃; wherein 12 mol %≦Li₂O+Na₂O+K₂O≦20 mol % and 0 mol %≦MgO+CaO≦10mol %. This alkali aluminosilicate glass is described in U.S. Pat. No.8,158,543 (Sinue Gomez et al., “Fining Agents for Silicate Glasses”).

Another exemplary alkali-aluminosilicate glass composition comprises atleast about 50 mol % SiO₂ and at least about 11 mol % Na₂O, and thecompressive stress is at least about 900 MPa. In some embodiments, theglass further comprises Al₂O₃ and at least one of B₂O₃, K₂O, MgO andZnO, wherein−340+27.1·Al₂O₃−28.7·B₂O₃+15.6·Na₂O−61.4·K₂O+8.1·(MgO+ZnO)≧0 mol %. Inparticular embodiments, the glass comprises: from about 7 mol % to about26 mol % Al₂O₃; from 0 mol % to about 9 mol % B₂O₃; from about 11 mol %to about 25 mol % Na₂O; from 0 mol % to about 2.5 mol % K₂O; from 0 mol% to about 8.5 mol % MgO; and from 0 mol % to about 1.5 mol % CaO. Theglass is described in U.S. Provisional Patent Application No.61/503,734, filed Jul. 1, 2011, to which U.S. patent application Ser.No. 13/533,298 claims the benefit, which published as U.S. PatentApplication Publication No. 2013/0004758 (Matthew J. Dejneka et al.,“Ion Exchangeable Glass with High Compressive Stress”), the contents ofwhich are incorporated herein by reference in their entirety.

Other types of glass compositions besides those mentioned above andbesides alkali-aluminosilicate glass composition can be used for the 3Dcover glass. For example, alkali-aluminoborosilicate glass compositionscan be used for the 3D cover glass. In some embodiments, the glasscompositions used are ion-exchangeable glass compositions, which aregenerally glass compositions containing small alkali or alkaline-earthmetals ions that can be exchanged for large alkali or alkaline-earthmetal ions. Additional examples of ion-exchangeable glass compositionscan be found in U.S. Pat. No. 7,666,511 (Ellison et al; 20 Nov. 2008),U.S. Pat. No. 4,483,700 (Forker, Jr et al.; 20 Nov. 1984), and U.S. Pat.No. 5,674,790 (Araujo; 7 Oct. 1997) and U.S. patent application Ser. No.12/277,573 (Dejneka et al.; 25 Nov. 2008), which published as U.S.Patent Application Publication No. 2009/0142568, Ser. No. 12/392,577(Gomez et al.; 25 Feb. 2009), which issued as U.S. Pat. No. 8,158,543,Ser. No. 12/856,840 (Dejneka et al.; 10 Aug. 2010), which published asU.S. Patent Application Publication No. 2011/0045961, Ser. No.12/858,490 (Barefoot et al.; 18 Aug. 18, 2010), which issued as U.S.Pat. No. 8,586,492, and Ser. No. 13/305,271 (Bookbinder et al.; 28 Nov.2010), which published as U.S. Patent Application Publication No.2012/0135226.

A three dimensionally shaped glass article, such as a 3D cover glass,made according to the process described herein can be used to cover anelectronic device having a flat display. The 3D cover glass will protectthe display while allowing viewing of and interaction with the display.The 3D cover glass has a front cover glass section for covering thefront side of the electronic device, where the display is located, andone or more side cover glass sections for wrapping around the peripheralside of the electronic device. The front cover glass section iscontiguous with the side cover glass section(s).

EXAMPLES

Various embodiments will be further clarified by the following examples.

Comparative Example 1

A glass sheet having Corning glass composition no. 2317 was shaped intoa three-dimensional shaped glass article using (1) a pressing processwith a three piece mold wherein the glass sheet under the flat areaplunger and the bend area plunger are heated to different temperaturesand (2) a conventional isothermal pressing process using a two piecemold wherein the glass sheet is heated uniformly across its entirelength. FIG. 11 compares the thermal cycle of the two processes. Thethree piece mold has a considerably shorter thermal cycle because thebottom mold has a much smaller temperature excursion than in theisothermal process. In the three piece mold process the mold cyclesbetween 550-570° C. and 620° C., with exception of the mold in the bendarea. In the conventional isothermal press process mold cycles from550-570° C. to 700° C., which is much larger, and therefore increasesboth the heat up and cooling time. This illustrates the benefit of usinga three-piece mold, which allows the temperature profile to vary acrossthe width of the glass sheet, over a two-piece mold.

Comparative Example 2

A simulation was run for shaping a glass sheet into a three-dimensionalshaped glass article using (1) a pressing process with a three-pieceporous mold, as shown for example in FIGS. 10A-10E and (2) a pressingprocess with a two-piece porous mold, as shown for example in FIGS.12A-12D. As can be seen in FIGS. 12A-12D a glass sheet 1100 iscompressed between a porous bottom mold 1110 having a shaping surface1112 with a flat area 1114 and a bend area 1116 and a porous top mold1120 having a shaping surface 1122 with a flat area 1124 and a bend area1126. Shaping surfaces 1112 and 1122 are complementary in shape. FIG. 13illustrates the pressure profile across the length of a 700 μm thickglass heated to 770° C. for the two piece mold and FIG. 14 illustratesthe pressure profile across the width of a 700 μm thick glass heated to770° C. for the three piece mold. As can be seen by comparing FIGS. 13and 14, in the process using the two-piece mold the glass sheet bucklesin the flat area, whereas in the process using the three-piece mold doesnot buckle. This again illustrates the benefit of using a three-piecemold, which allows the temperature profile to vary across the width ofthe glass sheet, over a two-piece mold because being able to control thetemperature profile prevents buckling of the glass in the flat region.

While the process, apparatuses, and compositions herein have beendescribed with respect to a limited number of embodiments, those skilledin the art, having benefit of this disclosure, will appreciate thatother embodiments can be devised which do not depart from the scope ofthe disclosure. Accordingly, the scope should only be limited by theattached claims.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. (canceled) 11.(canceled)
 12. An apparatus for making a three dimensionally shapedglass article, comprising: a mold having a shaping surface with adesired surface profile for the shaped glass article including a flatarea and a bend area; a flat area plunger positioned over the flat areaof the mold and having a shaping surface corresponding to the flat areaof the mold; a bend area plunger positioned over the bend area of themold and having a shaping surface corresponding to the bend area of themold; and a heater positioned to heat a region of a glass sheet placedover the bend area of the mold, wherein the flat area plunger and thebend area plunger move relative to one another.
 13. The apparatus ofclaim 12, wherein the mold, the flat area plunger, and the bend areaplunger are porous.
 14. The apparatus of claim 13, further comprising agas source connected to the porous mold, flat area plunger, and the bendarea plunger so that gas can flow through the porous mold, flat areaplunger, and bend area plunger to form a compressive gas layer above andbelow the glass sheet.
 15. The apparatus of claim 12, wherein the heateris incorporated in the bend area plunger.
 16. The apparatus of claim 12,wherein the heater is a radiant heater positioned adjacent the bend areaplunger.
 17. The apparatus of claim 12, wherein the bend area of themold comprises a first bend area and a second bend area, wherein thebend area plunger is a first bend area plunger arranged above the firstbend area of the mold, and wherein the apparatus further comprises asecond bend area plunger arranged above the second bend area of themold.
 18. The apparatus of claim 12, wherein the flat area of the moldcomprises a first flat area and a second flat area, wherein the flatarea plunger is a first flat area plunger arranged above the first flatarea of the mold, and wherein the apparatus further comprises a secondflat area plunger arranged above the second flat area of the mold. 19.(canceled)